The conventional support frame for a container trailer includes both a base frame which supports the container and a suspension frame which includes the wheel/axle assembly and the suspension system. Typically, the base frame and the suspension frame are separately fabricated and welded or bolted together prior to mounting of the container thereon. In at least a part of one or both of the fabrication phases, various sheet metal components are cut from sheets of metal, and they may be bent or otherwise fabricated into particular shapes or configurations. In the assembly phase, these components are located and fixed with respect to each other using assembly fixtures, and they are welded or otherwise joined to form the frame component. Then the base frame and the suspension frame are joined together and a container is mounted thereon. The techniques conventionally employed in the assembly phase rely heavily on a vast array of fixtures that are used to locate the individual frame components prior to being welded. These fixtures range in complexity from small tabletop welding jigs with simple locators to very complex electronically controlled motor driven units capable of holding large assemblies or subassemblies in place for welding. These fixtures cost many thousands of dollars to design and manufacture and also require ongoing maintenance to insure that they remain accurate and consistent with product improvement and other design changes. In addition, the locating of components with respect to each other by fixturing often results in errors in fit and weld integrity between the components. When fixturing is used to locate components with respect to each other, most of the welds required for the assembly of a frame structure must be made by human rather than robot welders. Furthermore, in an attempt to correct errors in fit between the components, large welds are often made to fill in the gaps between components. Such large welds may contribute increased weight and may cause heat distortion in the finished product. In addition, the fixtures for a new product require time to design and build. When a new prototype for a product is to be made, it is often necessary to build the fixtures for the design by hand. This process is slow, labor-intensive and expensive.
In recent years, there have been a number of developments aimed at improving the conventional manufacturing process. For example, flexible manufacturing systems and modular fixturing systems have been developed to handle an increase in product variations, especially as relates to custom fabricated products or the production of several products on a single production line. However, these systems have not attempted to reduce the extent to which fixturing is required in the manufacture of frames for container trailers.
It would be desirable if a manufacturing method and frame design for a trailer having a container mounted thereon could be devised that would reduce or minimize the number and complexity of the fixtures required for assembly. It would also be desirable if such a method and frame design could be devised that would reduce or minimize the risk of human error in the assembly process. It would also be desirable if such a method and frame design could be provided that would provide for more accurate fit of the various components, thus reducing the size of the welds required and reducing the effects of heat distortion due to such welds. It would also be desirable if such a method and frame design could be developed that would require fewer and less complex components than conventional designs.